Playing as Venice, I started a very early war with Milan to kick them out of North Italia. They proved to be pretty stubborn though, partially helped by their Sicilian allies who were hounding at my southern borders. I eventually kicked them back over the Alps (they had taken Dijon and Bern). I wanted to concentrate on a lengthy campaign against the Byzantine Empire though and didn't want to have to leave stacks of units in Italy to fend off any would-be re-invasions by Milan, and nor did I want to follow them across the Alps and expose my self to French and German aggression. So I simply pranced acrossed the alps, sacked Bern and then gifted it to the Pope. So now I have all the passes in the Alps sealed off with forts, and a papal "buffer" state between myself and my vengeful and warlike neighbours
Works pretty well, it's always a handy strategy if one of your neighbours is getting unduly aggressive but you don't want to/can't handle an all-out-war with them. Steal their territories on their border, and then gift them to the pope to create a buffer.